Parkinson's disease is a progressive disorder of the nervous system that affects movement. It develops gradually, sometimes starting with a barely noticeable tremor in just one hand. Parkinson's is often diagnosed based on movement and/or motor symptoms, such as a tremor. However, the disease may begin prior to the onset of movement and/or motor symptoms and it can often be difficult to distinguish between forms of Parkinsonism. Treatment of the disease may be more effective if treatment were to begin in the earliest stages of the disease. Additionally, understanding of the earliest stages and the progression of the disease require identification of individuals with the disease or at an increased risk of developing the disease prior to the onset of noticeable movement and/or motor symptoms. Additionally, to develop medications and/or other therapeutic treatments that effectively treat the disease, a technique for measuring disease progression is required. Effective measurements of disease progression will facilitate future clinical trials testing therapies for Parkinson's disease and Parkinsonism.